全文获取类型
收费全文 | 529篇 |
免费 | 16篇 |
国内免费 | 8篇 |
专业分类
化学 | 307篇 |
晶体学 | 4篇 |
力学 | 27篇 |
数学 | 52篇 |
物理学 | 163篇 |
出版年
2016年 | 5篇 |
2015年 | 6篇 |
2013年 | 11篇 |
2012年 | 14篇 |
2011年 | 47篇 |
2010年 | 32篇 |
2009年 | 13篇 |
2008年 | 16篇 |
2007年 | 25篇 |
2006年 | 23篇 |
2005年 | 25篇 |
2004年 | 43篇 |
2003年 | 27篇 |
2002年 | 24篇 |
2001年 | 19篇 |
2000年 | 30篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 4篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 13篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1971年 | 2篇 |
1969年 | 4篇 |
1964年 | 2篇 |
1959年 | 2篇 |
1958年 | 2篇 |
1957年 | 2篇 |
1936年 | 2篇 |
1935年 | 2篇 |
1924年 | 2篇 |
1923年 | 2篇 |
排序方式: 共有553条查询结果,搜索用时 15 毫秒
1.
李应求 《数学年刊A辑(中文版)》2003,(4)
在随机环境中马氏链的研究领域,引入了一类π-不可约、常返和瞬时性的概念,给出了π-不可约链是瞬时链的一个充要条件,引入了双无限随机环境中马氏链不变函数的概念,讨论了它们的存在性及基本性质。最后,利用不变函数的性质,给出了π-不可约链是瞬时链的一个判别准则,此准则与不变函数有关。 相似文献
2.
3.
The hydrocarbon discovery prediction problem is important to firms having to make decisions about the deployment of scarce exploration resources. Traditional methods for estimating the discovery rate rely on the completion of time consuming simulation experiments. A rapid approximation that does not require the completion of simulation exists and has been shown to have some promise as a prediction tool. This paper investigates the accuracy of the approximation method under a wide variety of distributional and drilling efficiency assumptions. The results indicate that the approximation produces predictions close to those of simulation under most of the tested conditions. This suggests that resource exploration firms could conveniently use the method for a wide variety of planning purposes without incurring the same costs in time and personnel required for simulation. 相似文献
4.
Novel mixed valence states have been obtained by the treatment of cobaltous ferrocyanides (Co+2FeII) and ferricyanides (Co+2FeIII) in an ozone flow. The CN stretching bands occur at 2085 cm–1 for Co+2FeII and at 2160 cm–1 for Co+2FeIII. After the ozonization process of Co+2FeII, an intense band approximately at 2125 cm–1 is detected. This intermediate band must correspond to a mixed valence state of the type: FeII–CN–Co2+–NC–FeIII Mössbauer spectra recorded in situ during the ozonization of Co+2FeII show the presence of two components: a doublet with isomer shift and quadrupole splitting values close to the cobalti ferricyanide and a very broad line for the mixed valence state. From the Mössbauer and infrared spectra of the aged samples of the Co+2FeII after ozonization, a relaxation process to the initial state of the samples is observed but the mixed valence state is stable. 相似文献
5.
6.
The use of novel water-in-oil microemulsions in microemulsion electrokinetic chromatography 总被引:3,自引:0,他引:3
We describe the novel use of water-in-oil (W/O) microemulsions to achieve unique separations in microemulsion electrokinetic chromatography (MEEKC). The choice and concentration of the buffer type, surfactant and co-surfactant were all examined and optimized. Separations of a range of neutral and acidic analytes was shown to be markedly different to that obtained by (oil-in-water) O/W MEEKC. Neutral solutes are separated by virtue of their solubility (log P) values in O/W MEEKC with the more water-insoluble solutes migrating last. This separation process does not occur in W/O, as neutral solutes are not separated in order of log P. 相似文献
7.
8.
9.
10.
Cui C Brynda M Olmstead MM Power PP 《Journal of the American Chemical Society》2004,126(21):6510-6511
Reaction of Ar'GeGeAr' (1) with an excess of Me3SiN3 gives the non-Kekulé, biradicaloid Ar'Ge(mu-NSiMe3)2GeAr' (3, Ar' = 2,6-Dipp2C6H3, Dipp = 2,6-i-Pr2C6H3) which has a planar Ge2N2Si2 array and pyramidal geometry at the germaniums. DFT calculations for the model MeGe(mu-NSiH3)2GeMe indicate no Ge-Ge bonding and a singlet ground state. The calculated energy difference between the optimized singlet and triplet states is 17.51 kcal/mol. 相似文献